I agree that this doesn't sound like an anal gland problem. Wrong
spot for that, but it well could be an allergy problem. I'd probably
keep an eye on it to see if it spreads to other places on the dog.
If this is making him very uncomfortable, I'd let the Vet see him
or suggest an ointment to clear it up. Good luck with Merilyn.

p.s. I love the gaelic saying in your sig, How true.